Florida Republican Sen. Marco Rubio and the Heritage Foundation are now at odds over a study released by the foundation on Monday that calculates that the cost of an immigration reform proposal partly authored by Rubio would add $6.3 trillion to America's deficit.

The immigration reform proposal hammered out by a bipartisan group of senators, including Rubio, offers a 13-year pathway to citizenship for 11 million illegal immigrants already in the U.S. and is expected to begin the Senate Judiciary Committee markup process on Thursday.

According to the calculations presented in the Heritage Foundation's study, the proposal is expected to amass a "lifetime fiscal deficit" of at least $6.3 trillion. These calculations are based on the assumption that immigrants would receive $9.4 trillion in government benefits and services but only pay $3.1 trillion in taxes.

In a report on Tuesday, however, Sen. Rubio said the conclusion reached by the foundation was unique and it holds that status among experts simply because its analysis is flawed.

Criticizing its failure to use dynamic scoring, Rubio told reporters, "Heritage, I think, is the king of dynamic scoring, and in many respects we've advocated for dynamic scoring here because of the positions that they've taken." Dynamic scoring is when economists take into account the tax revenue generated from greater economic activity

"They are the only group that's looked at this issue and reached the conclusion they've reached. Everybody else who has analyzed immigration reform understands that if you do it, and we do it right, it will be a net positive for our economy," he added.

He then argued that the flaw with the analysis is that it unfairly stereotypes immigrants as poor, uneducated government dependents.

"Their argument is based on a single premise, which I think is flawed," he said. "That is these people are disproportionately poor because they have no education and they will be poor for the rest of their lives in the U.S. Quite frankly, that's not the immigration experience in the U.S. That's certainly not my family's experience in the U.S.," he said.

Despite Sen. Rubio reportedly being a protégé and close friend of former South Carolina senator and new president of the Heritage Foundation Jim Demint, the organization shot back with a statement defending its study on Wednesday morning.

"Senator Rubio's family story is a testament to the American Dream. His parents' ability to scrimp and save and sacrifice for their children is something in which we all take pride. The story of the Rubios, in fact, makes the point we make with our study. They represent the immigration model that worked for America for centuries and one we need to get back to," noted the group.

Highlighting how the "Great Society programs" created the groundwork for the modern welfare state, the group noted in its statement that an increasing dependence on government has become a threat to the American Dream.

"That dependency has been devastating to our society; it has shattered communities, families, and individuals. It is now threatening the American Dream. This is true for all—native and immigrant alike, lawful or unlawful. We do not blame immigrants for being entrapped by that system; we blame the people who created that system. We especially blame people who now seek to expand it," said the foundation.